Lecherous, filthy and ambitious, the Siberian-born Grigory Rasputin achieved influence as a starets--a Russian Orthodox mystic and guru. Moynahan (Claws of the Bear) writes with authority about one of the century's least attractive power brokers, a man who owed his opportunities to a genetic legacy of Queen Victoria, whose daughters carried the blood disease of hemophilia into the next generation. One of the queen's German granddaughters became empress of Russia, and Alexis, the youngest child and sole male heir of Tsar Nicholas II, was a bleeder. Moynahan shows how Rasputin's hold over the empress, who dominated her husband, was a seeming power to heal, temporarily, the frail czarevich. Rasputin's influence, which he peddled everywhere, further tarnished a monarchy already riddled by incompetence and corruption. In some ways Rasputin was saintly (he urged the czar to keep out of the 1914 war, turned bribe money over to the needy and ransomed the innocent as well as the guilty out of jai); he was also treacherous and profligate. Yet he would not have thrived without the devoted Alexandra, stresses Moynahan. Though aristocratic conspirators attempted to stop Russia's wartime hemorrhaging by murdering Rasputin in December 1916, their gesture was ultimately useless, for revolution was imminent. Moynahan's version of this oft-told tale is less spellbinding than sordid. Illustrations not seen by PW. (Sept.)